Process for casting molten metal

ABSTRACT

Molten metal is poured from a melt container to a mold cavity defined by a molding material wherein the molding material in the region of the runner gate is of a higher density with respect to the rest of the molding material. A pouring lip protruding from the melt container seals in the region of the runner gate for delivering molten metal from the melt container to the mold cavity.

BACKGROUND OF THE INVENTION

The invention relates to a process and apparatus for casting moltenmetal wherein a casting mold containing molding material and a runnergate formed in the molding material is filled from a melt containerhaving at least one pouring lip having a closable outlet.

It is known in the prior art to employ metering devices for controllingthe flow of molten metal to a casting mold. In order to avoid theexpense of a metering device, which also requires appropriatemaintenance, German Patent DE-PS 2,811,055 discloses that a meltcontainer can be placed with its pouring lip directly onto the castingmold or the mold material contained therein, with the interposition of aseparating element therebetween. The separating element can be ofvarious different designs, such as a funnel-shaped element, lying on themold material in a corresponding depression and opening out at its lowerfunnel end into the gate of the casting mold. The separating element canalso be pot-shaped or be designed in any other suitable manner andarranged in a a corresponding depression.

The object of the present invention is to simplify this casting processby eliminating separating elements while achieving a higher metal yield.

SUMMARY OF THE INVENTION

The foregoing object is achieved by the present invention wherein aprocess for casting molten metal from a melt container to a mold cavitydefined by a molding material comprises providing a gate in the moldingmaterial for communicating a runner gate with the mold cavity,compressing the molding material in the region of the runner gatewhereby the molding material in the region is denser with respect to therest of the molding material, providing the melt container with apouring lip having a closeable outlet, an outlet bore and a profiledlower surface projecting from the melt container, sealing the profiledlower surface on the molding material in the region of the runner gate,and feeding molten metal from the melt container through the outlet andsaid outlet bore in the pouring lip to the runner gate, gate and moldcavity such that the liquid level of the molten metal in the meltcontainer decreases during the casting operation. The present inventionincludes an apparatus for carrying out the process.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in greater detail below with reference to thedrawings wherein

FIG. 1 shows a vertical section through the diagrammatically representeddevice for casting, in a position before the filling of the casting moldand

FIG. 2 shows the device shown in FIG. 1 in the position following thefilling of the casting mold.

DETAILED DESCRIPTION

According to FIGS. 1 and 2, the melt container 1 has at its base apouring lip 2 having the outlet bore 3, which extends through the latterand, together with a stopper rod 4, which can be vertically displacedusing a drive means (not shown in the drawing), forms the closeableoutlet 5. At that end of the pouring lip 2 which projects downwardsbeyond the base of the melt container, the pouring lip 2 has a level orprofiled lower surface 6.

The casting mold 7 contains mold material 8 in which a mold cavity 9 tobe filled with molten metal is formed. The runner gate 10 at the top ofthe casting mold is connected to the mold cavity 9 via the gate 11. In aregion 12 surrounding the runner gate 10, the molding material 8 is morehighly consolidated. This extra consolidation is preferably effected byincreased compaction of the mold material. A depression 13 is thenformed in this more highly compacted region 12, preferably beingproduced by milling in or forming in and at the base of the depressionhaving a surface 14 which is brought into surface contact with the lowerside 6 of the pouring lip 2 during casting. To avoid excessive loadingand possible breaking off of the mold material by the contact forcesbetween the mold and the outlet in the recompacted area, the surface 14of the depression 13 can and preferably is profiled or made such that itslopes slightly upwards and outwards. The cleanly worked or molded baseof this depression 13 permits satisfactory sealing between the mold 7, 8and the lower surface 6 of the pouring lip 2. After the parting of themold and the melt container, the depression takes up the molten materialremaining in the outlet bore 3 after the closure of the stopper 4. Italso serves to receive any subsequent flow of iron. The cross-section ofthe outlet bore 3 is greater than the cross-section of the gate 11 so asto ensure that the entire cross-section of the gate is completely filledand to ensure that any failure to achieve an absolutely accurateconnection between the outlet bore 3 and the gate 11 with mutuallyaligned axes, i.e. a slight lateral displacement, has no disadvantageouseffect with respect to the filling operation.

The casting mold 7 is placed on a baseplate 15, which rests on a rollertrack 16. Means, which are not shown in the drawing, are used to movethe melt container 1 in the vertical direction, making it possible topress the latter with adjustable force against the casting mold 7. It isof course conversely also possible for only the casting mold 7 to bearranged in a vertically moveable manner and to be pressed with acontrollable amount of pressure against the melt container 1. Contactduring the filling operation is maintained by a controlled amount offorce. This force is set such that the resulting surface pressure isless than the strength of the mold so that the mold is not damaged. Byreason of this controlled amount of force, the lower surface 6 of thepouring lip 2 and the surface 14 of the depression 13 are pressedagainst one another in a completely tight manner.

During casting, the casting mold is filled with the molten metal, withthe liquid pressure of the molten metal dropping up to the end of thecasting time. This means that prior to casting, the melt container 1 isfilled with at least enough molten metal to fill the casting mold andthe casting mold is filled with this at a pressure which drops as aresult of the lowering of the level of molten metal. Controlled loweringof the level of molten metal can be achieved using the stopper rod 4. Bymeans of the stopper rod 4 the outlet 5 is at least partially closed ata point in time shortly before the mold cavity 9 is completely filled,in order thereby to reduce the pressure surge caused by the movingmolten metal.

The volume of the outlet bore 3 in the pouring lip 2 is comparativelysmall and the filling of the mold cavity 9 in the casting mold 7 cantherefore be carried out by fully closing the outlet 5 because the gate11 and the depression 13 take up the quantity of molten metal stillpresent in the outlet bore 3 after closure and the system operates likea riser, the molten metal following up as a result of the shrinkagewhich occurs. In this way it is possible to ensure that there is nomolten metal remaining above the gate 11, i.e. in comparison withhitherto known casting processes, that is processes using pouring cups,a smaller quantity of molten metal is required, leading very quickly tolarge savings.

It is to be understood that the invention is not limited to theillustrations described and shown herein, which are deemed to be merelyillustrative of the best modes of carrying out the invention, and whichare susceptible of modification of form, size, arrangement of parts anddetails of operation. The invention rather is intended to encompass allsuch modifications which are within its spirit and scope as defined bythe claims.

We claim:
 1. A process for casting molten metal from a melt container toa mold cavity defined by a molding material comprising:(a) providing agate in the molding material for communicating a runner gate with saidmold cavity; (b) compressing the molding material in the region of therunner gate whereby said molding material in said region is denser withrespect to the rest of the molding material; (c) forming a depressionhaving a sealing surface in the region of the runner gate where saidmolding material is denser; (d) providing said melt container with apouring lip having a closeable outlet, an outlet bore and a profiledlower surface projecting from said melt container; (e) sealing saidprofiled lower surface on said sealing surface of said depression in theregion of the runner gate; and (f) feeding molten metal rom said meltcontainer through said outlet and said outlet bore in said pouring lipto said runner gate, gate and mold cavity such that the liquid level ofthe molten metal in said melt container decreases during the castingoperation.
 2. A process according to claim 1 wherein one of the lowerprofiled surfaces of the pouring lip and the surface of the depressionhave a profile in order to shift the contact pressure from the region.3. A process according to claim 1 including monitoring the change in themetal level in the melt container during the casting operation andclosing the outlet when there is no longer any change in the metallevel.
 4. A process according to claim 1 including partially closing theoutlet of the melt container prior to filling said mold cavity forreducing any pressure surge arising in the mold cavity due to the movingmolten metal.
 5. A process according to claim 1 including sealing thecasting mold and the melt container by relative movement of the castingmold and the melt container in a vertical relation to one another.
 6. Aprocess according to claim 8 wherein said depression is formed bymilling.